usakabe K

Real-time volumetric imaging of human heart without electrocardiographic gating by 256-detector row computed tomography: initial experience.

Objective: The feasibility of human cardiac imaging using a prototype 256-detector row cone-beam computed tomography (256CBCT) scanner without electrocardiographic gating was examined. Methods: Two healthy male volunteers were examined by contrast-enhanced 256CBCT. The number of detectors was 912 × 256, each measuring approximately 0.5 mm × 0.5 mm at the center of rotation. The craniocaudal coverage was approximately 100 mm after reconstruction by the Feldkamp-Davis-Kress algorithm. The effective time resolution was 500 milliseconds using a half-scan algorithm. Results: Serial enhancement of the left ventricular myocardium was detected. The right and left coronary arteries at proximal and distal segments were depicted without significant blurring. Although the left ventricular wall motion on cine images was not smooth over time, it was possible to measure ventricular volume and ejection fraction. Conclusions: Using the 256CBCT, it was possible to visualize the coronary arteries, myocardial perfusion, and ventricular contraction simultaneously during a single acquisition.

Left Ventricular Dysfunction on Exercise Long Term After Total Repair of Tetralogy of Fallot

BACKGROUND Excellent results regarding mortality are well recognized in the long-term period after intracardiac repair of tetralogy of Fallot. However, it is still unclear how postoperative sequelae affect cardiac performance during exercise. METHODS AND RESULTS Twenty-nine patients with tetralogy of Fallot were studied 16 +/- 2 years after intracardiac repair by use of radionuclide first-pass ventriculography with an ultra-high-sensitive gamma camera at rest and at peak exercise on a semi-upright bicycle ergometer. The results were compared with those from 10 age- and sex-matched control subjects. Left and right ventricular ejection fraction and absolute ventricular volume were measured at rest and peak exercise. Regional right ventricular wall motion and diastolic function of the left ventricle were also assessed. Cardiac output of tetralogy was normally preserved both at rest and during exercise. Nevertheless, the incremental response of left ventricular ejection fraction during exercise was depressed in the patients. Left ventricular ejection fraction during exercise was inversely correlated with the right ventricular end-diastolic volume and the severity of pulmonary regurgitation. Regional wall motion at the right ventricular outflow tract was not decreased in the patients. Left ventricular diastolic function was not impaired in the patients compared with control subjects. CONCLUSIONS Latent left ventricular dysfunction during exercise is related to an enlarged right ventricle due to pulmonary regurgitation after intracardiac repair of tetralogy. Careful follow-up is required in patients having significant pulmonary regurgitation.

In vivo evaluation of antithrombogenicity for ion implanted silicone rubber using indium-111-tropolone platelets

Abstract H2+, N2+, O2+, and Ne+ ion implantations into silicone rods were performed at 150 keV with doses ranging from 1 × 1017 to 3 × 1017 ions/cm2 to improve antithrombogenicity. The antithrombogenicity was tested by the superior vena cava (SVC) indwelling method for two days in rats with 111In-tropolone platelets and by the inferior vena cava (IVC) indwelling method for periods of one to seven weeks in dogs. Results of the SVC indwelling method showed that platelet accumulation on H2+ and O2+ implanted specimens decreased. In particular 1 × 1017 O2+/cm2 implantation caused both accumulation onto specimens and a decrease of the SVC. Macroscopic views of the ion implanted IVC specimens in dogs revealed little thrombus formation. It is concluded that ion implantation into silicone rod is a useful technique to improve its antithrombogenicity.

Sympathetic Denervation and Reinnervation After Arterial Switch Operation for Complete Transposition

BACKGROUND Sympathetic cardiopulmonary nerves arise from the cervical sympathetic trunks and the stellate ganglia and subsequently course along the origin of the great arteries and the coronary arteries to innervate the ventricles. Therefore, the sympathetic nerves may be obligatorily interrupted by the arterial switch operation (ASO) for complete transposition of the great arteries. METHODS AND RESULTS To demonstrate and characterize the possible sympathetic denervation, 51 patients after ASO, 4.8 years old (range, 1 month to 10.1 years), underwent [123I]metaiodobenzylguanidine (MIBG) imaging of the sympathetic nerve terminal. MIBG uptake to the heart was graded by quantitative analysis using the heart-to-mediastinum (H/M) ratio of MIBG uptake. A quantitative criterion for absent uptake of MIBG was set to 1.48 in the H/M ratio. Four patients < 1 month after ASO showed complete absence of MIBG uptake, which had been observed preoperatively. In contrast, 47 patients late after ASO (range, 15 months to 10.1 years) showed various degrees of uptake of MIBG. Patients operated on at < or =55 days of age showed positive MIBG uptake much more frequently than those operated on at later ages. Heart rate and rate-pressure product at peak exercise on a treadmill exercise test were significantly greater in patients with positive uptake than in those with absent uptake of MIBG. CONCLUSIONS Cardiac sympathetic nerves were denervated early after and reinnervated late after ASO. Neonatal ASO may be favorable to facilitate sympathetic reinnervation, which may affect exercise tolerance late after surgery.

Myocardial uptake of 111In monoclonal antimyosin Fab in detecting doxorubicin cardiotoxicity in rats. Morphological and hemodynamic findings.

BackgroundThe therapeutic value of doxorubicin (DOX) is limited by its cardiotoxicity, which is dose dependent. To improve the detection of such myocardial damage, this study was designed to determine whether the 111In antimyosin antibody Fab could serve as a marker for cardiotoxicity in treated versus control rats on the basis of comparative morphological and hemodynamic findings. Methods and ResultsDOX was administered by intravenous injection to rats at a dose of 3 mg·kg−1· week−1 for 5 weeks. Three weeks after the final injection, an intravenous dose of 111In antimyosin, 740 kBq (20 μCi), was administered, and tissue distribution of the radioisotope (percent kilogram dose per gram) was assessed in 48 hours. Myocardial uptake of radioactivity by both ventzicles was more prominent in the DOX-treated rats than in control rats (p < 0.001). The heart-to-blood and heart-to-lung uptake ratios were markedly higher in the treated rats than in controls (p < 0.001). As the severnty of the myocardial damage increased, there was a progressive increase in myocardial uptake. There was a strong correlation between the severity of myocardial damage and the ventricular end-diastolic pressure (r=0.84 and r=0.83 in the left and right ventricles, respectively). On microscopic immunoautoradiography of the DOX-treated heart, there was a specific immunolocalization of the radiotracer in the injured myocytes but no radioactivity in the control myocytes. Conclusions111In antimyosin antibody appears to be a useful immunoradiotracer in detecting cardiac damage induced by DOX administration and in assessing the severity of cardiotoxicity. These data reinforce the clinical observation that myocardial imaging using 111In antimyosin Fab is able to provide information to guide the course of patients receiving DOX treatment.

Scatter correction by two-window method standardizes cardiac I-123 MIBG uptake in various gamma camera systems.

Heart to mediastinum count ratio (H/M) has been commonly utilized as an indicator of myocardial I-123 MIBG uptake. However, normal ranges of H/M were markedly different among various gamma camera systems. The purpose of this study was to clarify whether scatter correction by two-window method standardizes H/M among various gamma camera systems.Methods: Scatter uncorrected and corrected MIBG imaging was acquired in phantom and human studies in combination with low energy high-resolution collimator (LEHR) and medium energy collimator (MEC). For scatter correction, energy window width of 159 keV±10% was applied to main window imaging and 193 keV±9.5% was applied to upper window imaging for scatter correction.Results: In phantom study, a significant difference was observed in uncorrected H/M among three gamma camera systems using LEHR or MEC (2.09±0.06 vs. 2.58±0.03 in GCA 7200 camera, 2.00±0.07 vs. 2.42±0.06 in DS7 camera and 2.16±0.04 vs. 2.67±0.07 in Vertex plus camera). However, there was no significant difference in corrected H/M among the three gamma camera systems, either with LEHR or MEC (2.70±0.07 vs. 2.69±0.07 in GCA 7200 camera, 2.66±0.05 in DS7 camera and 2.66±0.05 vs. 2.61±0.05 in Vertex plus camera). In human study, uncorrected H/M in DS7 camera with LEHC was significantly lower than that in GCA 7200 camera with MEC (1.60±0.37 vs. 1.85±0.54, N=14). In contrast, the difference was insignificant in corrected H/M (2.12±0.59 vs. 2.16±0.68). There was a very excellent correlation in corrected H/M between DS7 and GCA 7200 cameras (r=0.991, p<0.001).Conclusion: This study demonstrated that scatter correction by the two-window method standardizes the H/M in MIBG scintigraphy either with LEHR or MEC. Scatter corrected H/M can be applied to measure a standardized parameter of MIBG uptake in human clinical studies using various gamma camera systems.

Effects of Ion Implantation on Protein Adsorption onto Silicone Rubber

A study has been made on the surface wettability, atomic ratio, chemical structure, chemical bonding states and plasma protein adsorption of ion implanted silicone rubbers. C + -, N 2 + -, 0 2 + -, Ar + - and Na + -ion implantations were performed at an energy of 150 keV at room temperature. The doses ranged from 1x10 12 to 1x10 17 ions/cm 2 . Ion implantation caused the surface roughness to increase by 1–5 times. Surface wettability was estimated by means of a sessile drop method using water. With increasing ion dose, the contact angle of water decreased from 98.9° to 48.5°. However, if the sample was in the air, the contact angle of water returned to its initial valve in time elapsed. The results of XPS measurements showed that implanted elements were incorporated in a gaussian like distribution and host elements were redistributed in the polymer matrix. No change of binding energies of 0 1s , C IS , Si 2p and Si 2p can be observed upon ion implantation. Results of FT-IR-ATR showed that C + -, N 2 + -, 0 2 + -, and Ar + -ion implantation decomposed the original chemical bonds to form the new radicals. The amounts of new radicals are related to doses of implanted ions. In contrast, Na + -ion implantation hardly formed new radicals. The amount of albumin adsorbed onto 0 2 + -, Ar + -, N 2 + -, and C + - ion implanted silicone is less than that on unimplanted specimens, but more fibrinogen is adsorbed. Na + -ion implantation produced an increase in the amount of adsorbed albumin as the dose increased. In summary, Na+ion implantation produces effects that are attributable to the additional implanted constituent in the surface of the silicone, and 0 2 + -, N 2 + -, C + -, and Ar + -ion implantations primarily cause radiation effects on silicone rubber.

Long follow-up study in patients with prior myocarditis by radionuclide methods

SummaryTen patients with previous myocarditis were evaluated to determine cardiac conditions by Tl-201 myocardial perfusion imaging and stress radionuclide ventriculography during the follow-up of 18–102 (average 56) months; the results were compared with those from ten sex-and age-matched controls. Exercise capacity by supine bicycle ergometer was reduced in patients with myocarditis. Their resting left ventricular ejection fraction (LVEF) was 57.5%±3.9%, similar to that of controls. LVEF response to stress in myocarditis was abnormal with an increment of end-systolic volume, while in the controls LVEF increased significantly during stress. Seven of the eight patients with an abnormal ejection fraction response had constant Tl-201 perfusion defects.This study indicates that latent left ventricular dysfunction is present in patients with prior myocarditis and that nuclear study is useful for long-term follow-up.

Regional cardiac sympathetic reinnervation in transplanted human hearts detected by123I-MIBG SPECT imaging

The purpose of this study was to assess the regional cardiac sympathetic reinnervation late (≥1 year) after heart transplantation (HTX) by means of123I-MIBG (MIBG) scintigraphy. Eight patients with a pretransplantation diagnosis of idiopathic dilated cardiomyopathy underwent MIBG scintigraphy more than one year after HTX. The presence or absence of regional MIBG uptake was evaluated in each SPECT image, and global MIBG uptake was semi-quantitatively assessed by the heart to mediastinum ratio (H/M). Five of 8 patients had visible MIBG uptake in both planar and SPECT images (PU group), whereas 3 of 8 patients had no uptake, 2 of them after a period of 2 years, and one of them as long as 5 years after HTX, respectively (NU group). Positive regional MIBG uptake involved the basal anterior region in all 5 patients, the basal septal region in 4 patients, the basal lateral region in 3 patients and the basal posterior region in 1 patient. The H/M value was 1.24±0.10 in the PU group and 1.09±0.03 in the NU group. In conclusion, MIBG SPECT can detect regional sympathetic reinnervation, indicating that basal septal and lateral regions next to the basal anterior are more likely to be reinnervated, but reinnervation is much less likely to occur in the midventricular and apical regions.

Myocardial dysfunction and depressed fatty acid metabolism in patients with cyanotic congenital heart disease

BackgroundMyocardial contractile dysfunction has been frequently observed in adolescents or adults with cyanotic congenital heart disease. Impaired energy metabolism may be present in such dysfunctional myocardium.Methods and ResultsTo evaluate the findings of myocardial free fatty acid metabolism, and its relations to ventricular wall motion and myocardial perfusion in cyanotic congenital heart disease, we performed a combined study of iodine 123-labeled 15-(p-iodophenyl)-3-(R,S)-methylpentadecanoic acid (BMIPP) scintigraphy, thallium scintigraphy, and contrast cineangiography in seven patients with single right or left ventricle. The results showed that wall motion was reduced in 17 of 35 ventricular segments (49%), which were mostly identical in location to decreased BMIPP uptake. The severity of BMIPP uptake deficit correlated positively with the degree of impairment of wall motion. On the other hand, thallium uptake was abnormal only in 5 of 35 segments (14%), and the severity of the perfusion defect did not correlate with the degree of wall motion abnormality.ConclusionsContractile dysfunction in cyanotic heart disease was primarily linked to impaired free fatty acid metabolism rather than to myocardial scar as represented by perfusion defect on thallium imaging.